Thermoplastic resin composition

ABSTRACT

The present invention relates to a thermoplastic resin composition which has an improved impact resistance while maintaining mechanical properties such as strength and rigidity. In the present invention, a thermoplastic resin (A) is mixed with a polytetrafluoroethylene-containing mixed powder (B) consisting of a polytetrafluoroethylene (b1) having a particle diameter of 10 μm or less and an organic polymer (b2). In this case, the polytetrafluoroethylene-containing mixed powder (B) is mixed so that the amount of a polytetrafluoroethylene component is from 0.0001 to 20 parts by weight based on 100 parts by weight of the thermoplastic resin (A), and a polymer having an epoxy group was used as the organic polymer (b2). The thermoplastic resin composition of the present invention can be widely used in the fields of automotive parts, electric and electronic parts, and precision instrument parts.

TECHNICAL FIELD

The present invention relates to a thermoplastic resin composition whichhas an improved impact resistance while maintaining mechanicalproperties such as strength and rigidity.

This application is based on Japanese Patent Application No. 2000-79131,filed in Japan, the content of which is incorporated herein byreference.

BACKGROUND ART

Thermoplastic resins have been widely used in the fields of automotiveparts, electrical and electronic parts, and precision instrument partsbecause they are superior in ease of processing, mechanical properties,and physical and chemical properties.

However, because the impact strength of the thermoplastic resin is low,improvement is required.

Many proposals have been made to improve the impact strength of thethermoplastic resin. Among these proposals, a method of mixing asilicone-acrylic composite rubber prepared by grafting a vinyl monomerhaving an epoxy group described in Japanese Patent No. 264113 is arelatively superior method.

However, this method has a drawback in that superior intrinsicproperties such as rigidity and heat resistance of the thermoplasticresin are impaired when mixing a rubber in an amount required to obtaina high impact strength.

DISCLOSURE OF THE INVENTION

The present invention has been made to solve the problems describedabove, and an object thereof is to provide a resin composition, whichhas improved impact strength, by the addition of a smaller amount of arubber component while maintaining excellent intrinsic properties suchas rigidity and heat resistance of the thermoplastic resin.

To achieve the above object, the present inventors have intensivelyreaserched and have found that the impact strength is markedly improvedby the addition of a small amount of a rubber component when adding apolytetrafluoroethylene-containing mixed powder comprisingpolytetrafluoroethylene particles having a particle diameter of 10 μm orless and an organic polymer having an epoxy group to a thermoplasticresin. Thus, the present invention has been completed.

The gist of the present invention lies in a thermoplastic resincomposition comprising a thermoplastic resin (A) and apolytetrafluoroethylene-containing mixed powder (B) consisting of apolytetrafluoroethylene (b1) having a particle diameter of 10 μm or lessand an organic polymer (b2), wherein thepolytetrafluoroethylene-containing mixed powder (B) is mixed so that theamount of the polytetrafluoroethylene component is from 0.0001 to 20parts by weight based on 100 parts by weight of the thermoplastic resin(A), and the organic polymer (b2) has an epoxy group.

In that case, the organic polymer is preferably a rubber-like polymerhaving an epoxy group.

Furthermore, the rubber-like polymer is preferably a polyorganosiloxanegraft copolymer which is prepared by graft-polymerizing a compositerubber comprising a polyorganosiloxane rubber and a polyalkyl(meth)acrylate rubber with one or more vinyl monomers containing atleast one epoxy group-containing vinyl monomer.

The thermoplastic resin (A) preferably contains, as a main component,one or more thermoplastic resins selected from polyester resin,polyamide resin, polyarylene sulfide resin, and polyolefin resin.

BEST MODE FOR CARRYING OUT THE INVENTION

Various resins can be employed as the thermoplastic resin (A) used inthe present invention, and are preferably those containing, as a maincomponent, one or more thermoplastic resins selected from polyesterresin, polyamide resin, polyarylene sulfide resin, and polyolefin resin.

As used herein, the polyester resin refers to a polyester resin obtainedby the polycondensation reaction of one or more dicarboxylic acidsselected from terephthalic acid, isophthalic acid,naphthalenedicarboxylic acid, 4,4′-diphenyldicarboxylic acid,diphenyletherdicarboxylic acid, α, β-bis (4-carboxyphenoxy)ethane,adipic acid, sebacic acid, azelaic acid, decanedicarboxylic acid,dodecanedicarboxylic acid, cyclohexanedicarboxylic acid and dimer acid,or ester-forming derivarives thereof, and one or more glycols selectedfrom ethylene glycol, propylene glycol, butanediol, pentanediol,neopentyl glycol, hexanediol, octanediol, decanediol, cyclohexanedimethanol, hydroquinone, bisphenol A,2,2-bis(4′-hydroxyethoxyphenyl)propane, xylene glycol, polyethyleneether glycol, polytetrafluoroethylene ether glycol, and aliphaticpolyester oligomer having a hydroxyl group at both terminals. Thepolyester resin may be either a homopolyester or a copolyester. Inaddition to the compounds described above, as the comonomer componentconstituting the copolyester, for example, a hydroxycarboxylic acid suchas glycolic acid, hydroxy acid, hydroxybenzoic acid, hydroxyphenylaceticacid or naphthylglycolic acid, and a lactone compound such aspropiolactone, butyrolactone, caprolactone or valerolactone can be used.A polyester having a branched or crosslinked structure, which uses apolyfunctional ester-forming component such as trimethylolpropane,trimethylolethane, pentaerythritol, trimellitic acid, trimesic acid orpyromellitic acid, may be used as long as it can maintain thethermoplasticity. It also includes a polyester copolymer containing ahalogen, which has, as a substituent, a halogen compound in aromaticcarbons and uses a compound having an ester-forming group such asdibromoterephthalic acid, tetrabromoterephthalic acid,tetrachloroterephthalic acid, 1,4-dimethyloltetrabromobenzene,tetrabromobisphenol A, or an ethylene or propylene oxide adduct oftetrabromobisphenol A. Also a polyester elastomer constituting a blockcopolymer of a high-melting point segment and a low-melting pointsegment can be used. The polyester elastomer includes, for example, ablock copolymer of a hard segment composed mainly of an alkylterephthalate unit and a soft segment composed of an aliphatic polyesteror polyether. As the component (A), these polyester resins can be usedalone or in combination thereof. Particularly preferred polyester resinsinclude polybutylene terephthalate, polyethylene terephthalate, and acopolymer composed thereof as a main repeating unit. Examples of thecomonomer component constituting the copolymer include isophthalic acid,bisphenol A, 2,2-bis(β-hydroxyethoxyphenyl)propane and2,2-bis(β-hydroxyethoxytetrabromophenyl)propane.

The polyamide resin is not specifically limited and may be amino acidlactam, or an entire polymer composed of diamine and dicarboxylic acid,which can be subjected to melt polymerization and melt processing.

Specific examples of the polyamide resin used in the present inventioninclude the following resins. They are (1) polycondensates of an organicdicarboxylic acid having 4 to 12 carbon atoms and an organic diaminehaving 2 to 13 carbon atoms, for example, polyhexamethyleneadipamide[6,6 nylon] as a polycondensate of hexamethylenediamine and adipic acid,polyhexamethyleneazelamide [6,9 nylon] as a polycondensate ofhexamethylenediamine and azelaic acid, polyhexamethylenesebacamide [6,10nylon] as a polycondensate of hexamethylenediamine and sebacic acid,polyhexamethylenedecanoamide [6,12 nylon] as a polycondensate ofhexamethylenediamine and dodecanedioic acid, andpolybis(4-aminocyclohexyl)methanedodecane as a polycondensate ofbis-p-aminocyclohexylmethane and dodecanedioic acid; (2) polycondensatesof ω-amino acid, for example, polyunedecaneamide [11 nylon] as apolycondensate of ω-aminoundecanoic acid; and (3) ring-openingpolymerization products of lactam, for example, polycapramide [6 nylon]as a ring-opening polymerization product of ε-aminocaprolactam andpolylauric lactam [12 nylon] as a ring-opening polymerization product ofε-aminolaurolactam. Among these resins, polyhexamethyleneadipamide (6,6nylon), polyhexamethyleneazelamide (6,9 nylon) and polycapramide (6nylon) are preferably used.

In the present invention, a polyamide resin prepared from adipic acid,isophthalic acid, and hexamethylenediamine can also be used.Furthermore, a blend of two or more polyamide resins such as a mixtureof 6 nylon and 6,6 nylon can be used.

The polyamide (1) can be prepared, for example, by the polycondensationof an organic dicarboxylic acid having 4 to 12 carbon atoms and anorganic diamine having 2 to 13 carbon atoms in an equimolar ratio. Ifnecessary, the organic dicarboxylic acid can be used in an amount largerthan that of the organic diamine so that carboxyl groups in thepolyamide resin are in excess of the amino groups. Conversely, theorganic dicarboxylic acid can be used in an amount smaller than that ofthe organic diamine so that amino groups in the polyamide resin are inexcess of the carboxyl groups.

Specific examples of the organic dicarboxylic acid include adipic acid,pimelic acid, suberic acid, sebacic acid and dodecanoic diacid. Specificexamples of the organic diamine include hexamethylenediamine andoctamethylenediamine.

In the same manner as described above, the polyamide resin (1) can beprepared from a derivative capable of producing carboxylic acid such asester or carboxylic acid chloride, and a derivative capable of producingamine such as amine salt.

The polyamide resin (2) can be prepared, for example, by polycondensinga ω-amino acid with heating in the presence of a small amount of water.Usually, a small amount of a viscosity stabilizer such as acetic acid isadded.

The polyamide resin (3) can be prepared, for example, by performingring-opening polymerization of a lactam with heating in the presence ofa small amount of water. Generally, a small amount of a viscositystabilizer such as acetic acid is added.

The polyarylene sulfide resin, which can be used in the presentinvention, is a polymer having, as a main constituent unit, a repeatingunit represented by the general formula: —(Ar—S)— and may be composedonly of a straight-chain structure, and may have a crosslinked structureas long as it has melt processability. In the above general formula, Arrepresents a group represented by the following formula or at least onegroup having 1 to 8 substituents such as halogen or methyl group on thearomatic ring.

wherein X represents —SO₂—, —CO—, —O—, or a main-chain alkylene grouphaving 1 to 5 carbon atoms, which may have a lower alkyl side chain.

Examples of the polyolefin resin used in the present invention includethose containing, as a main component, a homopolymer or copolymer of anolefin monomer obtained by radical polymerization or ion polymerization,a copolymer of a larger amount of an olefin monomer and a smaller amountof a vinyl monomer, or a copolymer of an olefin monomer and a dienemonomer. These polyolefin resins are used alone or in combination.Conventionally known catalysts such as a Ziegler catalyst, chromecatalyst and metallocene catalyst are used.

Examples of the olefin monomer as used herein include ethylene,propylene, butene-1, hexene-1, decene-1, octene-1 and4-methyl-pentene-1. Among these olefin monomers, ethylene and propyleneare particularly preferred. Specific examples of the homopolymer orcopolymer of the olefin monomer include low density polyethylene,ultra-low-density polyethylene, ultra-super-low density polyethylene,linear low density polyethylene, high density polyethylene, ultrahighmolecular weight polyethylene, polypropylene, ethylene-propylenecopolymer, polymethylpentene and polybutene. These olefin polymers areused alone or in combination. Among these olefin monomers, a polyolefinresin containing, as a main component, a mixture of two or more kindsselected from the group consisting of polyethylene, polypropylene andethylene-propylene copolymer is particularly preferred.

It is necessary that the polytetrafluoroethylene-containing mixed powder(B) used in the present invention comprise a polytetrafluoroethylene(b1) having a particle diameter of 10 μm or less and an organic polymer(b2), and that polytetrafluoroethylene not be in the form of anagglomerate having a particle diameter of 10 μm of more than in thepowder and the organic polymer is a polymer having an epoxy group.

As the polytetrafluoroethylene-containing mixed powder, preferred arethe following polytetrafluoroethylene-containing mixed powders (i) to(iii):

-   (i) polytetrafluoroethylene-containing mixed powder obtained by    mixing an aqueous dispersion of polytetrafluoroethylene particles    having a particle diameter of 0.05 to 1.0 μm with an aqueous    dispersion of organic polymer particles and solidifying the mixture    or powderizing the mixture using a spray drying means;-   (ii) polytetrafluoroethylene-containing mixed powder obtained by    polymerizing a monomer constituting an organic polymer in the    presence of an aqueous dispersion of polytetrafluoroethylene    particles having a particle diameter of 0.05 to 1.0 μm and    solidifying the mixture or powderizing the mixture using a spray    drying means; and-   (iii) polytetrafluoroethylene-containing mixed powder obtained by    emulsion-polymerizing a monomer having an ethylenically unsaturated    bond in a mixed dispersion of an aqueous dispersion of    polytetrafluoroethylene particles having a particle diameter of 0.05    to 1.0 μm and aqueous dispersion of organic polymer particles and    solidifying the mixture or powderizing the mixture using a spray    drying means.

The aqueous dispersion of polytetrafluoroethylene particles having aparticle diameter of 0.05 to 1.0 μm used to obtain thepolytetrafluoroethylene-containing mixed powder (B) used in the presentinvention is obtained by polymerizing a tetrafluoroethylene monomer bymeans of the emulsion polymerization using a fluorine-containingsurfactant.

During the emulsion polymerization of polytetrafluoroethylene particles,a fluorine-containing olefin such as hexafluoropropylene,chlorotrifluoroethylene, fluoroalkylethylene or perfluoroalkyl vinylether and a fluorine-containing alkyl (meth)acrylate such asperfluoroalkyl (meth)acrylate can be used as a copolymerizationcomponent as long as properties of polytetrafluoroethylene are notimpaired. The content of the copolymerization component is preferably10% by weight or less based on tetrafluoroethylene.

Typical examples of the commercially available raw material of thepolytetrafluoroethylene particle dispersion include “Fluon AD-1” and“Fluon AD936” manufactured by Asahi Fluoropolymers Co., Ltd.; “PolyflonD-1” and “Polyflon D-2” manufactured by Daikin Industries, Ltd.; and“Teflon 30J” manufactured by Du Pont-Mitsui Fluorochemicals Co., Ltd.

The organic polymer (b2) used to obtain thepolytetrafluoroethylene-containing mixed powder (B) used in the presentinvention is a polymer having an epoxy group and is not specificallylimited as long as it is effective to improve the impact strength of thethermoplastic resin. The organic polymer is particularly preferably arubber-like polymer.

The rubber-like polymer refers to a polymer which is in the form ofrubber at room temperature and preferably has a glass transitiontemperature of −20° C. or less. Specific examples thereof include is adiene copolymer such as polybutadiene, polyisoprene,ethylene-propylene-ethylidene norbornene copolymer,ethylene-propylene-dicyclopentadiene copolymer,ethylene-propylene-5-ethylidene-2-norbornene copolymer,acrylonitrile-butadiene copolymer or isoprene-isobutylene copolymer; aacrylic rubber such as a copolymer of n-butyl acrylate and an acrylateester monomer capable of copolymerizing with n-butyl acrylate; asilicone rubber including dimethylsiloxane unit as a main componet; andsilicone-acrylic composite rubber of silicone and acrylate. Among theserubbers, a silicone-acrylic composite rubber is preferred.

When the organic polymer is a polymer having an epoxy group, thedispersibility in the thermoplastic resin (A) can be improved. As therubber-like polymer having an epoxy group, for example, core-shellparticles having an epoxy group or an elastomer having an epoxy groupcan be used.

As used herein, the core-shell particles having an epoxy group refer toa copolymer obtained by polymerizing an epoxy group-containing vinylmonomer and, if necessary, the other copolymerizable vinyl monomer inthe presence of the rubber-like polymer.

Examples of the elastomer having an epoxy group include straight-chaincopolymers such as ethylene-glycidyl methacrylate copolymer andethylene-vinyl acetate-glycidyl methacrylate copolymer; and graftcopolymer composed of the straight-chain copolymer as a main chain andpolystyrene or methyl polymethacrylate as a side chain.

Among these rubber-like polymers, particularly preferred is apolyorganosiloxane polymer obtained by graft-polymerizing a compositerubber composed of a polyorganosiloxane rubber and a polyalkyl(meth)acrylate rubber with one or more vinyl monomers containing atleast one epoxy group-containing vinyl polymer.

The content of polytetrafluoroethylene in thepolytetrafluoroethylene-containing mixed powder (B) used in the presentinvention is preferably from 0.1 to 90% by weight.

In the resin composition of the present invention, thepolytetrafluoroethylene-containing mixed powder (B) consisting of apolytetrafluoroethylene (b1) having a particle diameter of 10 μm or lessand an organic polymer (b2) is mixed in an amount ofpolytetrafluoroethyrene of 0.0001 to 20 parts by weight based on 100parts by weight of the thermoplastic resin (A). When the amount is lessthan 0.0001 parts by weight, the effect of improving the impact strengthis poor. On the other hand, when the amount exceeds 20 parts by weight,the fluidity during melting is lowered too much.

As long as original purposes are not impaired, more desired physicalproperties and characteristics can be obtained by appropriately mixingthe resin composition of the present invention with various additives,for example, pigments and dyes; reinforcers and fillers, such as glassfibers, metal fibers, metal flakes and carbon fibers; phenolantioxidants such as 2,6-di-butyl-4-methylphenol and4,4′-butylidene-bis(3-methyl-6-t-butylphenol); phosphite antioxidantssuch as tris(mixed, mono and diphenyl) phosphites and diphenylisodecylphosphite; sulfur antioxidants such as dilauryl thiodipropionate,dimyristyl thiodipropionate and distearyl thiodipropionate;benzotriazole ultraviolet absorbers such as2-hydroxy-4-octoxybenzophenone and2-(2-hydroxy-5-methylphenyl)benzotriazole; photostabilizers such asbis(2,2,6,6)-tetramethyl-4-piperidinyl; electostatic agents such ashydroxyalkylamine and sulfonic acid salt; lubricants such asethylenebisstearylamide and metal soap; and flame retardants such astetrabromophenol A, decabromophenol oxide, TBA epoxy oligomer, TBApolycarbonate oligomer and antimony trioxide.

If necessary, more desired physical properties and characteristics canbe obtained by appropriately mixing the thermoplastic resin compositionof the present invention with polyphenylene ether resin; polyamideresin; polycarbonate resin; vinyl copolymers such as polymethylmethacrylate (PMMA); polyolefin resins such as vinyl chloride resin, ABSresin, styrene resin, polyethylene and polypropylene; and olefin rubberssuch as ethylene-propylene copolymer, ethylene-butene-1 copolymer,ethylene-propylene-dicyclopentadiene copolymer,ethylene-propylene-5-ethylidene-2-norbornene copolymer,ethylene-propylene-1,4-hexadiene copolymer, ethylene-vinyl acetatecopolymer and ethylene-butyl acrylate copolymer.

The thermoplastic resin composition of the present invention is preparedby mixing the above essential components and, if necessary, arbitrarycomponents in a predetermined amount and kneading the mixture using aconventional kneader such as roll, Banbury mixer, single-screw extruderor twin-screw extruder. The thermoplastic resin composition ispreferably pelletized.

By using the thermoplastic resin composition thus obtained, it becomespossible to obtain a molded article, which has rigidity and high impactstrength and is free from macroagglomerates of polytetrafluoroethyleneand also has excellent surface characteristics, by various moldingmethods.

Examples of the method of processing the thermoplastic resin compositionof the present invention include, but are not limited to, injectionmolding, calendering, blow molding, extrusion molding, thermoforming,foaming and melt spinning.

Examples of useful molded articles obtained from the thermoplastic resincomposition of the present invention include, but are not limited to,injection molded articles, sheets, films, hollow molded articles, pipes,square bars, profile, thermoforms, foams and fibers.

EXAMPLES

In the following descriptions, “parts”,“%” are by weight unlessotherwise specified. Various physical properties were measured by thefollowing procedures.

-   (1) Solid content: The solid content was determined after drying a    particle dispersion at 170° C. for 30 minutes.-   (2) Particle size distribution: Using a sample solution prepared by    diluting a particle dispersion with water, the particle size    distribution was measured by a dynamic light scattering method    (Model ELS800 manufactured by Otsuka Electronics Co., Ltd.,    temperature: 25° C., scatter angle: 90 degrees).-   (3) Izod impact strength: Using test pieces (with a notch) having a    thickness of 3.2 mm obtained by injection molding, the Izod impact    strength was measured at 23° C. in accordance with ASTM D256.-   (4) Flexural modulus: Using test pieces having a thickness of 6.4 mm    obtained by injection molding, the flexural modulus was measured in    accordance with ASTM D790.-   (5) Heat deformation temperature: The heat deformation temperature    was measured under a load of 1.820 MPa by the method defined in ASTM    D648.-   (6) Appearance: The appearance of the surface of each test piece    obtained by injection molding was visually observed and the    appearance was evaluated by the following criteria.-   ◯: no lumpiness on the surface-   X: lumpiness observed on the surface

The following commercially available products were used as thethermoplastic resins (A-1, A-2), the rubber-like polymer (M-1) having anepoxy group and a portion of other materials.

-   Thermoplastic resin (A-1): polybutylene terephthalate resin (“Tafpet    PBT N1000”, manufactured by Mitsubishi Rayon Co., Ltd.)-   Thermoplastic resin (A-2): polybutylene terephthalate resin    (“Dianite PA210”, manufactured by Mitsubishi Rayon Co., Ltd.)    Rubber-like polymer (M-1) having an epoxy group: ethylene-glycidyl    methacrylate copolymer (“Bond Fast E”, manufactured by Sumitomo    Chemical Industries Co., Ltd.)    <Preparation of Polytetrafluoroethylene-containing Mixed Powder    (B-1)>

2.0 Parts of γ-methacryloyloxypropyldimethoxysilane and 98.0 parts ofoctamethylcyclotetrasiloxane were mixed to obtain 100 parts of asiloxane mixture. To the siloxane mixture, a solution prepared bydissolving 1 part of sodium dodecylbenzenesulfonate in 300 parts ofdistilled water was added and, after stirring in a homomixer at 10000rpm for 2 minutes, the solution was passed twice through a homogenizerunder a pressure of 30 MPa to obtain a stable pre-mixed organosiloxanelatex. Separately, 10 parts of dodecylbenzenesulfonic acid and 90 partsof distilled water were charged in a separable flask equipped with acondenser and a stirring blade to prepare an aqueous 10% benzenesulfonicacid solution. While maintaining the resulting aqueous solution at 85°C., the stable pre-mixed organosiloxane latex was added dropwise over 2hours and, after 3 hours have passed since the completion of thedropwise addition, the reaction solution was cooled. The resultingreduction product was allowed to stand at room temperature for 12 hoursand then neutralized with an aqueous sodium hydroxide solution.

The silicone latex (L-1) thus obtained had a solid content of 18.1% anda weight-average particle diameter of 32 nm.

55.2 Parts of the silicone latex (L-1) was collected and charged in aseparable flask equipped with a stirring blade, and then 149.8 parts ofdistilled water was added. After replacing the atmosphere in theseparable flask with nitrogen and raising the temperature to 50° C., amixed solution of 90 parts of n-butyl acrylate (BA), 0.045 parts ofallyl methacrylate and 0.36 parts of cumene hydroperoxide was added. Amixed solution of 0.001 parts of ferrous sulfate, 0.003 parts ofdisodium ethylenediaminetetraacetate, 0.2 parts of Rongalite and 5 partsof distilled water was added and the radical polymerization wasinitiated, and then the mixture was maintained at an inner temperatureof 50° C. for 2 hours to obtain a silicone-acrylic composite rubberlatex (S-1).

The resulting rubber latex (S-1) had a solid content of 33.2% and theparticle size distribution exhibited a single peak, and theweight-average particle diameter was 72 nm.

As the polytetrafluoroethylene particle dispersion, “Fluon AD936”manufactured by Asahi Fluoropolymers Co., Ltd. was used. “Fluon AD936”has a solid content of 63.0% and contains polyoxyethylene alkyl phenylether in an amount of 5 parts based on 100 parts ofpolytetrafluoloethylene. The particle size distribution of “Fluon AD936”exhibited a single peak and the weight-average particle diameter was 290nm.

To 833 parts of “Fluon AD936”, 1167 parts of distilled water was addedto obtain a 26.2% polytetrafluoroethylene particle dispersion (F-1). Thepolytetrafluoroethylene particle dispersion (F-1) contains 25%polytetrafluoroethylene particles and 1.3% polyoxyethylene alkyl phenylether.

247 Parts of the composite rubber latex (S-1) was collected and chargedin a separable flask equipped with a stirring blade. After replacing theatmosphere in the separable flask with nitrogen and raising thetemperature to 60° C., a mixed solution of 8 parts of glycidylmethacrylate (GMA) and 0.04 parts of cumene hydroperoxide was addeddropwise over 8 minutes. After the mixture was maintained at an innertemperature of 60° C. for one hour and 16 parts of apolytetrafluoroethylene particle dispersion (F-1) was added, a mixedsolution of 10 parts of methyl methacrylate (MMA) and 0.05 parts ofcumene hydroperoxide was added dropwise over 15 minutes, the mixture wasmaintained at an inner temperature of 60° C. for 2 hours and the radicalpolymerization was completed to obtain a latex of apolytetrafluoroethylene-containing mixed powder (B-1). The latex (B-1)thus obtained had a solid content of 37.0% and a weight-average particlediameter of 120 nm.

The latex (B-1) was added in an aqueous calcium chloride solution havinga concentration of 2% at 40° C. so that a weight ratio of the latex tothe aqueous solution was 1:2, and then solidified by heating to 90° C.After repeating the operation of washing with water, the solid componentwas separated and dried at 80° C. for 24 hours to obtain a dry latexpowder (B-1).

Very thin slices obtained by forming the dry latex powder (B-1) into astrip using a pressing machine at 250° C. and cutting using a microtomewere observed by a transmission electron microscope without staining. Asa result, polytetrafluoroethylene was observed as the dark portion, andno agglomerate having a size of more than 10 μm was observed.

<Preparation of Polytetrafluoroethylene-containing Mixed Powders (B-2,B-3)>

In the same manner as in case of the preparation of thepolytetrafluoroethylene-containing mixed powder (B-1), except that theamount of grycidyl methacrylate or methyl methacrylate to be addeddropwise was set as shown in Table 1, drypolytetrafluoroethylene-containing mixed powders (B-2, B-3) wereobtained.

Very thin slices obtained by forming the dry latex powders (B-2, B-3)into a strip using a pressing machine at 250° C. and cutting using amicrotome were observed by a transmission electron microscope withoutstaining. As a result, polytetrafluoroethylene was observed as the darkportion, and no agglomerate having a size of more than 10 μm wasobserved.

<Preparation of Polytetrafluoroethylene-containing Mixed Powders (B-4,B-5)>

In the same manner as in case of the preparation of thepolytetrafluoroethylene-containing mixed powder (B-1), except that theamount of (F-1) to be added in the preparation of thepolytetrafluoroethylene-containing mixed powder (B-1) was set as shownin Table 1, dry polytetrafluoroethylene-containing mixed powders (B-4,B-5) were obtained.

Very thin slices obtained by forming the dry latex powders (B-4, B-5)into a strip using a pressing machine at 250° C. and cutting using amicrotome were observed by a transmission electron microscope withoutstaining. As a result, polytetrafluoroethylene was observed as the darkportion, and no agglomerate having a size of more than 10 μm wasobserved.

<Preparation of Rubber-like Polymer (M-2) Having an Epoxy Group>

In the same manner as in the case of the preparation of thepolytetrafluoroethylene-containing mixed powder (B-1), except that (F-1)used in the preparation of the polytetrafluoroethylene-containing mixedpowder (B-1) was not used, a dry powder of a rubber-like polymer (M-2)having an epoxy group was obtained.

TABLE 1 Composition (Parts) Si BA GMA (F-1) PTFE MMA B-1 8.2 73.8 8 16 410 B-2 8.2 73.8 2 16 4 16 B-3 8.2 73.8 10 16 4 8 B-4 8.2 73.8 8 8 2 10B-5 8.2 73.8 8 32 8 10

Examples 1 to 8 and Comparative Examples 1 to 7

Thermoplastic resins (A-1, A-2) and a polytetrafluoroethylene-containingmixed powder were mixed in a mixing ratio shown in Table 2 and themixture was extruded at a screw revolution speed of 200 rpm using atwin-screw extruder (Model ZSK30, manufactured by WERNER & PFLEIDERERCO) to prepare pelletized thermoplastic resin compositions.

Test pieces for measurement of various physical properties were madefrom the resulting thermoplastic resin compositions using an injectionmolding machine, and then the impact strength, the flexural modulus, theheat deformation temperature (HDT) and the appearance were evaluated.The results are shown in Table 2.

For comparison, thermoplastic resin compositions obtained by extrudingonly the thermoplastic resin (Comparative Examples 1 and 7),thermoplastic resin compositions mixed with M-1 (Comparative Examples 2to 4), a thermoplastic resin composition mixed with M-2 (ComparativeExample 5) and a thermoplastic resin composition mixed with a finepolytetrafluoroethylene powder (CD123, manufactured by Asahi ICI Co.,Ltd.) (Comparative Example 6) were evaluated in the same manner. Theresults are shown in Table 3.

The cylinder temperature of the extruder and the injection moldingmachine was controlled to 240° C. for PBT and 280° C. for PET, while thedie temperature was controlled to 80° C. for PBT and 120° C. for PET.

TABLE 2 Examples 1 2 3 4 5 6 7 8 Composition (Parts) A-1 100 100 100 100100 100 100 A-2 100 B-1 5 10 20 10 B-2 10 B-3 10 B-4 10 B-5 10 M-1 M-2CD123 Impact strength (J/m) 190 830 1300 790 810 800 800 580 Flexuralmodulus (GPa) 2.40 2.25 2.00 2.23 2.23 2.20 2.32 2.07 HDT (° C.) 61 5852 56 56 55 59 57 Appearance ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯

TABLE 3 Comparative Examples 1 2 3 4 5 6 7 Composition (Parts) A-1 100100 100 100 100 100 A-2 100 B-1 B-2 B-3 B-4 B-5 M-1 5 10 20 M-2 10 10CD123 1 Impact strength (J/m) 34 90 140 490 150 150 29 Flexural modulus(GPa) 2.59 2.00 1.84 1.61 2.03 2.04 2.40 HDT (° C.) 65 55 51 40 54 54 65Appearance ◯ ◯ ◯ ◯ ◯ X ◯

Example 9 and Comparative Example 8

100 Parts of 6,6 nylon (UBE 66 Nylon 2020B, manufactured by UBEINDUSTRIES, LTD.) as a thermoplastic resin and 15 parts of thepolytetrafluoroethylene-containing mixed powder B-2 were mixed and themixture was pelletized at a cylinder temperature of 250° C. using atwin-screw extruder (Model ZSK30, manufactured by WERNER & PFLEIDERERCO). After drying the resulting pellets, test pieces for measurement ofvarious physical properties were made from the dried pellets at thecylinder temperature of 260° C. and the die temperature of 75° C. usingan injection molding machine, and then the impact strength, the flexuralmodulus, the heat deformation temperature and the appearance wereevaluated. The heat deformation temperature was measured under a load of0.455 MPa.

For comparison, 6,6 nylon alone was evaluated. The results are shown inTable 4.

TABLE 4 Example 9 Comparative Example 8 6,6 nylon (Parts) 100 100 B-2(Parts) 15 — Impact strength (J/m) 460 48 Flexural modulus (GPa) 2.352.85 Heat deformation temperature 221 230 (° C.) Appearance ◯ ◯

Example 10 and Comparative Example 9

100 Parts of polyphenylene sulfide (Tohprene T-4, manufactured byTohprene Ltd.) as a thermoplastic resin and 15 parts of thepolytetrafluoroethylene-containing mixed powder B-1 were mixed and themixture was pelletized at a cylinder temperature of 300° C. using atwin-screw extruder (Model ZSK30, manufactured by WERNER & PFLEIDERERCO). After drying the resulting pellets, test pieces for measurement ofvarious physical properties were made from the dried pellets at thecylinder temperature of 300° C. and the die temperature of 140° C. usingan injection molding machine, and then the impact strength, the flexuralmodulus, the heat deformation temperature and the appearance wereevaluated.

For comparison, polyphenylene sulfide (Tohprene T-4, manufactured byTohprene Ltd.) alone was evaluated. The results are shown in Table 5.

TABLE 5 Example 10 Comparative Example 9 Polyphenylene sulfide (Parts)100 100 B-1 (Parts) 15 — Impact strength (J/m) 410 35 Flexural modulus(GPa) 2.75 3.20 Heat deformation temperature 109 120 (° C.) Appearance ◯◯

Industrial Applicability

The thermoplastic resin composition of the present invention can be usedfor various purposes because it exhibits a high impact strength by theaddition of a small amount of a rubber and is also superior in surfacecharacteristics of the resulting molded article.

The present invention may be embodied in other specific forms withoutdeparting from the spirit or essential characteristics thereof. Thepresent embodiment is therefore to be construed in all respects asillustrative and not restrictive, the scope of the present inventionbeing indicated by the appended claims rather than by the foregoingdescription and all changes which fall within the meaning and range ofequivalency of the claims are therefore intended to be embraced therein.

1. A thermoplastic resin composition comprising a thermoplastic resin (A) and a polytetrafluoroethylene-containing mixed powder (B) comprising: a polytetrafluoroethylene (b1) having a particle diameter of 10 μm or less and an organic polymer (b2), wherein the polytetrafluoroethylene-containing mixed powder (B) is mixed so that the amount of a polytetrafluoroethylene component is from 0.0001 to 20 parts by weight based on 100 parts by weight of the thermoplastic resin (A), and the organic polymer (b2) is a polyorganosiloxane graft copolymer which is prepared by graft-polymerizing a composite rubber comprising a polyorganosiloxane rubber and a polyalkyl (meth)acrylate rubber with one or more vinyl monomers containing at least one epoxy group-containing vinyl monomer.
 2. The thermoplastic resin composition according to claim 1, wherein the thermoplastic resin (A) comprises, as a main component, one or more thermoplastic resins selected from the group consisting of polyester resin, polyamide resin, polyarylene sulfide resin, and polyolefin resin.
 3. A polytetrafluoroethylene-containing mixed powder comprising a polytetrafluoroethylene having a particle diameter of 10 μm or less and an organic polymer, wherein the organic polymer is a polyorganosiloxane graft copolymer which is prepared by graft-polymerizing a composite rubber comprising a polyorganosiloxane rubber and a polyalkyl (meth)acrylate rubber with one or more vinyl monomers containing at least one epoxy group-containing vinyl monomer.
 4. A thermoplastic resin composition comprising a thermoplastic resin (A) and a polytetrafluoroethylene-containing mixed powder (B) consisting of a polytetrafluoroethylene (b1) having a particle diameter of 10 μm or less and an organic polymer (b2), wherein the polytetrafluoroethylene-containing mixed powder (B) is mixed so that the amount of a polytetrafluoroethylene component is from 0.0001 to 20 parts by weight based on 100 parts by weight of the thermoplastic resin (A), and the organic polymer (b2) is a rubber-like polymer having an epoxy group.
 5. A thermoplastic resin composition comprising a thermoplastic resin (A) and a polytetrafluoroethylene-containing mixed powder (B) consisting of a polytetrafluoroethylene (b1) having a particle diameter of 10 μm or less and an organic polymer (b2), wherein the polytetrafluoroethylene-containing mixed powder (B) is mixed so that the amount of a polytetrafluoroethylene component is from 0.0001 to 20 parts by weight based on 100 parts by weight of the thermoplastic resin (A), and the organic polymer (b2) is a polymer having an epoxy group; wherein the thermoplastic resin (A) is at least one or more thermoplastic resins selected from the group consisting of polyester resin, polyamide resin, polyarylene sulfide resin, and polyolefin resin.
 6. The thermoplastic resin composition according to claim 5, wherein the organic polymer is a polyorganosiloxane graft copolymer which is prepared by graft polymerizing a composite rubber comprising a polyorganosiloxane rubber and a polyalkyl (meth)acrylate rubber with one or more vinyl monomers containing at least one epoxy group containing vinyl monomer. 